1. Field of Invention
This invention relates to sequencing valves and is particularly directed to sequencing valves which are operated by pressure of fluid supplied to the inlet thereof.
2. Prior Art
Sequencing valves are frequently used in irrigation systems and the like to distribute fluid, such as water, from a single supply source to one or another of a plurality of irrigations points, such as sprinklers. Thus, for example, a golf course may have a single water supply pipe supplying a sequencing valve which passes the water, in turn, to sprinklers serving a respective one of the fairways of the golf course. When it is desired to switch the system to irrigate a different fairway, the sequencing valve is stepped to its next position to pass the water to the sprinklers serving the new fairway. The stepping action of the sequencing valve is conventionally accomplished by turning the water supply "OFF" and "ON" to provide a pressure pulse to which the sequencing valve responds by advancing one step. Unfortunately, many of the prior art sequencing valves are highly complex devices which are expensive to produce and require considerable maintenance. Still other prior art sequencing valves have been unreliable in operation and have failed to properly regulate the flow of water in a desired manner. Also, some prior art sequencing valves have been electrically actuated. However, for large irrigation systems, such as farms, golf courses and the like, this requires running extensive lengths of electrical wiring, which is expensive and is subject to breakage or weathering, thereby adding an additional maintenance factor. A search in the U.S. Patent Office has revealed the following:
______________________________________ U.S. Pat. No. INVENTOR ISSUED ______________________________________ 3,730,208 D. E. Lewis May 1, 1973 3,759,283 T. Maeda Sep. 18, 1973 4,305,417 W. W. Bell, Jr. Dec. 15, 1981 4,492,247 G. H. Lockwood Jan. 8, 1985 ______________________________________
Each of these reference is subject to the limitations set forth above. Thus, none of the prior art sequencing valves have been entirely satisfactory.